Days before their 45th wedding anniversary bash, a couple receives news that destabilizes the harmony they’ve enjoyed for so long.

When can a fact change the substance of our reality, and when can the substance of our reality override a fact? It’s an interesting question, and one worth pondering with the dazzling Charlotte Rampling as we travel with her across 45 Years.

Here we meet Kate Mercer, one half of Kate and Geoff, the couple being feted with a 45th wedding anniversary bash mere days away – and a genuine celebration it promises to be, honoring their clearly affectionate and still-vibrant bond. Life has, of course, shown the passage of time, but that time has resulted in a home with history and character, routines worn deep into sustaining rhythms, and a romance that while mature, has not lost its friendship and playfulness. Kate and Geoff speak the spare words of those who understand each other without them, and Kate fully recognizes the enviable privilege of having reached this milestone able to look back on a happy life well spent, with comfortable appreciation and acceptance of the time remaining.

One day Geoff receives a bit of news, an update regarding a half-century-old event long concluded; it’s a disconcerting blast from the past, but they discuss it and the matter returns to rest before teatime. Yet what appeared to be a formality seems to send Geoff reeling in ways he struggles to minimize, turning Kate’s contentment into concern and ultimately into excavation, as a bit of news begins to take shape as a true ghost of youth long past, bringing with it a threat never before considered.

There’s a Law & Order episode (I paraphrase) in which a character laments, “She was only there because I asked her to stop for milk on the way home… she’s dead because of me,” to which the prosecutor responds, “No, she’s dead because the defendant stabbed her.” And then there’s Fiddler on the Roof, in which Tevye queries his arranged-marriage wife of twenty-five years, asking “Do you love me?” – prompting Golde to think about it for the first time, reflect upon their life together, and realize that yes, she does. Or remember The Painted Veil, in which after much agony all around Walter and Kitty recover from her affair only to find she’s pregnant with no clue to fatherhood, and they realize that now, the DNA genuinely does not matter.

So where does a fact fit – and why does it fit there? Where do our actions hold us responsible for outcome, and where does Life take over in a way we just have to deal with without misplaced guilt? How does a fact fit into and relate to other facts of reality, removing our choice and requiring us to bloom where we are planted? Is such a life an equal (or even better) alternative, or is it a counterfeit? Where does honesty fit in, both about the fact and also about the way it affects us? When does what you don’t know not hurt you, and when does it? Where does one person’s truth become another’s deception? What is forgivable, and under what circumstances – and what is not? And what does one do with the answers one finds? These are important questions to ponder, and worth pondering before Life forces the ponder, because facts are important, and where they fit even more so.

Such are the questions Kate faces as she faces this bit of news (as well as others even bigger which I shan’t spoil for you), and in the hands of screenwriter/director Andrew Haigh, the understated and excellent Tom Courtenay, and the Oscar-nominated Rampling, the excavation is nothing short of riveting (Rampling is my personal pick for Best Actress 2015, hands down). As Kate puts her lovingly tended home, comforting routines, and playful partnership through strict scrutiny, 45 Years almost reaches the timbre of a thriller. At one point it’s just Kate staring at a screen, but Haigh’s direction and Rampling’s reactions are so powerful that one almost expects to see an apparition materialize behind her. Never has the past haunted so palpably. Never has the gentle click of a slide carousel sounded so bone chilling, or felt like the twist of a knife.

So what does Kate do with what she finds (what will Geoff do with what Kate finds)? What facts of her own will she bring to bear? Does this fact that wafted in one day change everything, or does it ricochet off her reality into the mists of history? If you’ve ever had to re-evaluate your understanding of a person or situation, you’ll resonate with her story. And if not, all the more reason to see two of the best performances 2015 has to offer.